Device for powdering printed products

ABSTRACT

For powdering printed products it is proposed that they be moved through a nip formed by a powder application roller (38) and a support roller (32). Those two rollers have axial circumferential recesses (52, 54) which are each able to receive at least part of a gripper rod (24) moving a printed product and which are synchronized with the movement of a gripper rods. At a location upstream of the nip in the direction of rotation, powder is applied to the circumferential surface of the application roller (38) by a nozzle strip (62), which powder is then transferred in the passage nip from the application roller to the printed products.

The invention relates to an apparatus for powdering printed productsaccording to the precharacterising clause of claim 1.

In known powdering apparatus of that kind, the metered powder streamdelivered from the powder reservoir is distributed in a carrier gasstream, and the powder mist so produced is fed to a nozzle stripextending transversely across the path over which the printed productsare conveyed.

Owing to the gripper rods which move the printed products, that nozzlestrip has to be arranged at a correspondingly large distance away fromthe conveying surface of the printed products. That is disadvantageousinter alia because a proportion of the powder mist produced escapes intothe printing machine. In addition, only some of the powder particlesdirected towards the printing inks cling to the printing inks which havenot yet dried completely.

By means of the present invention an apparatus according to theprecharacterising clause of claim 1 is to be so developed that improvedefficiency in the distribution of the metered powder stream over thesurface of the printed products is achieved therewith.

That problem is solved according to the invention by a powderingapparatus having the features mentioned in claim 1.

In the case of the powdering apparatus according to the invention,powder particles are applied by a powder feeding element to the surfaceof an application roller.

The application roller has a circumference corresponding to the distancebetween successive gripper rods and is furthermore provided with arecess which is able to receive a gripper rod. The movement of theapplication roller is so synchronized with that of the gripper rods thatgripper rods and recess arrive at the same time in the gap createdbetween the application roller and the support element which supportsthe reverse side of the printed products. Since the application rollercooperates with the printed side of the printed products in a frictionalconnection, powder particles held on the circumferential surface of theapplication roller are transferred to the printed products veryeffectively. Since the feeding element, which in turn applies the powderparticles to the circumferential surface of the application roller, isarranged outside the path of the gripper rods, it is not necessary toprovide a large gap between its outlet end and the circumferentialsurface of the application roller.

The powdering apparatus according to the invention therefore operatesvery reliably with reduced powder consumption and with a reduction inthe surrounding portions of the printing machine.

Advantageous developments of the invention are indicated in subclaims.

With the development of the invention according to claim 2, especiallygentle transport of the printed products in the region of theapplication roller is obtained. In addition, the perpendicular forceprevailing in the nip and acting on the printed products can be selectedto be greater than when the reverse side of the printed products issupported by a plate-shaped stationary support element with slidingfriction.

The development of the invention according to claim 3 is alsoadvantageous with regard to exerting a relatively high application forceof the powder particles.

As a result of the development of the invention according to claim 5,the printed products do not have to travel through sharp curves in theregion of the powdering apparatus.

The development of the invention according to claim 6 is advantageouswith regard to removing small residual amounts of powder which becomedetached from the surface of the application roller on the way betweenthe feeding element and the nip between the application roller and thesupport element and of powder particles that are not properlytransferred from the feeding element to the application roller.

The development of the invention according to claim 7 ensures that,between the feeding element and the path of the application rollerbetween the application roller and the support element, thecircumferential surface of the application roller is surrounded with asmall clearance, which is similarly advantageous with regard to avoidingthe escape of powder particles.

As a result of the development of the invention according to claim 8,the powder particles are held non-positively on the circumferentialsurface of the application roller.

The development of the invention according to claim 9 provides theadvantage that the powder particles held by the application roller arereliably released from the surface of the roller and transferred to theprinted products at the nip.

The development of the invention according to claim 10 allows theapplication roller to be coated with powder particles very evenlyutilising the proven technology used for direct dusting of printedproducts.

The alternative for applying powder particles to the circumferentialsurface of the application roller given in claim 11 has the advantagethat the particles are applied mechanically and there is no outflowingcarrier gas carrying a residue of powder particles with it. A furtheradvantage of the apparatus according to claim 11 is that, when coatingthe outer surface of the application roller with powder particles, anyresidual amounts of powder particles are taken into account, in otherwords a transfer of the powder particles carried by the applicationroller to the printed products that is only partial, as is desirable inspecial applications, does not lead to local double coating of theapplication roller when the surface regions coated with the residue passby the feeding element again.

In a powdering apparatus according to claim 12, there is improvedsealing of the feeding element with respect to the downstream region ofthe apparatus.

As a result of the development of the invention according to claim 13,in the case of polarisable or chargeable powder particles an improvedtransfer thereof from the feeding element to the circumferential surfaceof the application roller is obtained.

The development of the invention according to claim 14 allows a targetedpartial coating of the printed products with powder particles. Regionsof the printed products where there is no fear of sticking toneighbouring sheets of a stack can therefore remain uncoated.

The development of the invention according to claim 15 allows thepowder-coated regions and the powder-free regions of the printedproducts to be specified in a simple manner.

Determination of the powder pattern on the surface of the printedproducts can be carried out simply automatically if the printing inkdistribution on the printed product is measured with a sensor strip, asspecified in claim 16, and the output signals of that sensor strip areused to produce the control signals stored in the pattern memory, whichcontrol signals actuate the individual feeding element segments.

The development of the invention according to claim 17 not only allowsprinted and unprinted surfaces to be distinguished but also (for exampleby reference to the ink) allows those regions that carry two or morelayers of ink to be distinguished from regions printed with only asingle layer of ink. In many printed products it may be sufficient notto powder the regions covered with only a single layer of ink if thoseregions are only relatively small in size and are thus spaced in anycase from a neighbouring printed sheet by neighbouring, highermultiple-ink regions.

The development of the invention according to claim 18 also serves topowder the printed products in regions in a controlled manner.

The development of the invention according to claim 19 allows both sidesof the printed products to be equally powdered. Powdering of the printedproducts on two sides can sometimes be more advantageous than a thickone-sided powdering of only one surface of a printed product that isprinted on both sides since, in that way, both sides are treatedsymmetrically and are thus exactly the same in feel and in shine.

The invention is described in detail below with the aid of illustrativeembodiments and with reference to the drawings, in which:

FIG. 1: shows a longitudinal schematic section through the outlet end ofa printing machine in which dusting of the printed products with powdertakes place;

FIGS. 2 and 3: are each a view similar to FIG. 1, showing a modifiedapparatus for powdering printed products;

FIG. 4: is a schematic view of the connection of various parts of theapparatus shown in FIGS. 1 to 3 to supply units;

FIG. 5: is a view similar to FIG. 1, showing a modified apparatus forpowdering printed products;

FIG. 6: is a circuit diagram of a control unit for a controllable powderfeeding element of the apparatus shown in FIG. 5;

FIG. 7: is a circuit diagram of a modified control unit for acontrollable powder feeding element of the apparatus shown in FIG. 5;and

FIGS. 8 and 9: are views similar to FIG. 1, showing further, modifiedapparatuses for powdering printed products.

A printing machine, of which only the end section at the outlet side isshown in FIG. 1, has lateral frame plates 10 which are connected bycross-members 12.

Supported in the frame plates 10 are axles 14, 16 each carrying twoaxially spaced chain wheels 18 and 20, respectively. Conveyor chains 22which are correspondingly spaced apart in the axial direction and whichcarry at regular intervals gripper rods 24, of which only two are shownby way of example in FIG. 1, run over the chain wheels 18, 20. In theillustrated end section of the printing machine, the conveying path forthe printed products takes an S-shaped course over a stacking station 26on which the finished printed products are collected to form a stack 28.

In the ascending portion of the conveying path, a powder applicationhead 30 is arranged at the printed side of the printed products.Provided opposite it, in relation to the conveying path of the printedproducts, is a support roller 32 which is supported in the frame plates10 by means of a shaft 34.

The application head 30 has a housing 36 in which an application roller38 rotates. The latter is supported in the frame plates 10 by means of ahollow shaft 40. Extending through the hollow shaft 40 in a sliding fitis a carrier pipe 42 which carries an eccentric blowing pipe 44extending in the axial direction. The blowing pipe 44 is connected (seeFIG. 4) via a 2/2 solenoid valve 46 and a pressure regulator 48 to acompressed air line 50.

An axial recess 52 is provided in the support roller 32;correspondingly, the application roller 38 has an axial recess 54. Therecesses 52, 54 have a depth which is so calculated that they are ableto receive a gripper rod 24 on their own if necessary. Thecircumferential length of the recesses 52, 54 corresponds to the size ofa gripper rod 24 measured in the conveying direction, plus a safetymargin.

The support roller 32 is rigidly connected to a toothed wheel 56 whichcooperates with the underside of the conveyor chain 22. The applicationroller 38 is connected to a toothed wheel 58, which is shown in FIG. 1as lying in the plane of the drawing but which, in reality, is offsetfrom the plane of the drawing and meshes with the second conveyor chainwhich is not shown in the drawing. Accordingly, the support roller 32and the application roller 38 are driven in opposite directions ofrotation, the phase position of the two rollers being so adjusted thatthe recesses 52, 54 meet in the nip and enclose from both sides agripper rod 24 running synchronously into the nip.

The application roller 38 is therefore able to run with a small amountof clearance or in frictional connection on the support roller 32.

Arranged in the housing 36 surrounding the application roller 38 is anozzle strip 62 which comprises a distributor pipe 64 and a plurality ofnozzles carried thereon.

A continuously adjustable stream of powder is delivered from a powderreservoir 68 by a metering device 70 which may, for example, include aplate vibrator. The stream of powder is fed to the one inlet of a mixernozzle 72, the second inlet of which is connected via a 2/2 solenoidvalve 74 and a pressure regulator 76 to a compressed air line 50. Theoutlet of the mixer nozzle 72, at which a powder mist stream isobtained, is connected to the inlet of the distributor pipe 64. Wisps ofpowder mist thus leave the delivery openings of the nozzle strip 62,which delivery openings face the circumferential surface of theapplication roller 38. The powder particles contained therein cling atleast to some extent to the outer surface of the application roller 38,as is indicated in FIG. 1 at 80.

The adhesive power of the powder particles on the outer surface of theapplication roller 38 can be improved by making the circumferential wallof the application roller 38, shown at 82, from a suitable material,especially a plastics material, in which the powder particles (usuallycorn starch particles having an average particle diameter of about from10 to 20 μm) adhere well.

In order to prevent powder mist from leaving from the downstream endsection of the housing 36, a blowing strip 84 is provided upstream ofthe nozzle strip 62 viewed in the direction of rotation, which blowingstrip is connected via a pressure regulator 86 to the compressed airline 50.

As can also be seen from FIG. 1, the housing 36 has in the portionthereof lying downstream of the nozzle strip 62 a wall part 88 that iscoaxial with the hollow shaft 40 and extends at a small distance abovethe outer surface of the application roller 38. The downstream end ofthe circumferential wall 82 is sufficiently far away from the conveyingsurface through which the gripper rods 24 pass that the latter rununhindered past the end of the circumferential wall 82.

Approximately at the middle of the circumferential extent of thecircumferential wall 82, a suction pipe 90 is connected to the housing36, which suction pipe 90 is connected (see FIG. 4) to a suction fan 92.In that manner, the carrier gas of the mist still containing residualpowder particles is sucked away and free powder particles not carried onthe surface of the application roller 38 are prevented from leaving atthe upstream end of the housing 36. The stream of air sucked in by thefan 92 and the partial vacuum thereby produced in the interior of thehousing 36 is small, so that no powder particles are sucked off thesurface of the application roller 38.

The powder particles reaching the nip are then transferred to theprinting inks as they come into contact with the still tacky printingink of the printed products, and pass on with the printed products,while the surface of the application roller 38, which is now free ofpowder particles again, returns to the nozzle strip 62 to be re-coatedwith powder.

In the modified illustrative embodiment of a powdering apparatus shownin FIG. 2, a wire electrode 94 is provided downstream of the nozzlestrip 62 viewed in the direction of rotation, which electrode isconnected (see FIG. 4) to one terminal of a high-voltage generator 96.The second terminal thereof is connected to the machine earth, to whichthe hollow shaft 40 is also connected. Normally, the electrode 94 is atpositive potential and the field formed between the electrode 94 and theapplication roller 38 assists migration of the powder particles 80towards the roller surface.

In the illustrative embodiment shown in FIG. 3, the circumferential wall82 of the application roller 38 is made from a sintered material thepores of which are so dimensioned that no powder particles are able toenter the wall material but the wall as a whole is still air-permeable.

Arranged on the inside of the circumferential wall 82 is a suction box98 which is connected (see FIG. 4) via a pressure regulator 100 to asuction machine 102. That connection is not shown in FIG. 3; it is madeby a passage through the second end of the hollow shaft 40.

By applying a partial vacuum to the circumferential portion of theapplication roller 38 located between the nozzle strip 62 and theupstream end of the housing 36, good adherence of the powder particlesto the roller surface is obtained. The application roller can thereforecarry a greater amount of powder per unit area. After disconnecting thepartial vacuum downstream of the rearward end of the suction box 98viewed in the direction of rotation and as a result of the air deliveredby the blowing pipe 44 an effective transfer of the powder particlesfrom the application roller 38 to the printed products is ensured.

FIG. 5 shows a powdering apparatus derived from that shown in FIG. 1.For each of the nozzles 66 there is a provided a solenoid valve 104which controls the connection between the nozzle and the distributorpipe 64. The various solenoid valves are connected to associated outputterminals of a control unit 106 (see FIG. 6).

The control unit 106 operates in dependence upon the output signals of asensor strip 108 which is arranged upstream of the powder applicationhead 30, transversely across the conveying path of the printed products.The sensor strip 108 comprises a plurality of sensor elements 110, eachof the sensor elements 110 lying in a plane that is parallel to theplane of the drawing and that passes through an associated one of thenozzles 66.

The sensor strip 108 lies at a distance in front of the nip formed bythe support roller 32 and the application roller 38, which distancecorresponds to the involute of that circumferential portion of theapplication roller 38 which lies between the nozzle strip 62 and thenip.

Owing to the synchronized movement of the application roller 38 and theconveyor chains 22, the portion of a printed product situated in the nipis therefore covered with those powder particles which were delivered bythe nozzle strip 62 at the point in time when the corresponding surfaceregion of the printed product was under the sensor strip 108.

The control unit 106 may therefore consist, as shown in FIG. 6, simplyof discriminator circuits 112 which are associated with the individualsensor elements and which, in the simplest case, merely determinewhether the surface region of the printed product lying under the sensorelement is printed or not. More complicated discriminator circuits canexamine whether the region of the surface of the printed product justbeing scanned by the associated sensor element has been printed withone, two or more printing inks.

The discriminator circuits 112 generate an output signal wheneveranalysis of the printing reveals that powdering is necessary in thesurface region just tested. After being amplified in amplifiers 114, theoutput signal of the discriminator circuits 112 can then be useddirectly to actuate the solenoid valves 104.

In a modified illustrative embodiment, a modified control unit is usedwhich makes it possible also to select a different position of thesensor strip 108, in addition to the specific position of the sensorstrip shown in FIG. 5 by continuous lines which is coordinated with theposition of the nozzle strip 62; that different position may arise fromthe necessity of arranging other elements, for example an additionaldrier, upstream of the powder application head 30. A sensor striparranged in that manner is shown by broken lines in FIG. 5.

As can be seen from FIG. 7, the outputs of the discriminator circuits112-1 to 112-N associated with the sensor elements 110-1 to 110-N(N=number of nozzles 66 of the nozzle strip 62) are for that purposeconnected via first inputs of OR gates 116 to a read-in register 118 ofa pattern memory 120. The number of memory cells is at least equal tothe number obtained by dividing the length of a printed sheet by thelength of the measuring region of a sensor element 110.

A rotary encoder 122 which is coupled to the hollow shaft 40 isconnected to the input of an analogue-to-digital converter 124. Theoutput thereof is connected to one input of a digital summing circuit126 which receives at its second input via a line 128 a digital phasesignal corresponding to the difference in the position of the sensorstrip 108 at that point of the conveying path of the printed productswhich is the same distance away from the nip as is the nozzle strip 62.In the circumstances shown in FIG. 5, the phase signal corresponds tothe difference in position between the sensor strip shown by solid linesand the sensor strip drawn in broken lines.

The output of the summing circuit 126 is connected to the one input ofan OR gate 130 the output of which is connected to an address register132 of the pattern memory 120.

The memory cells of the pattern memory 120 are further connected via aread-out register 134 to the inputs of the amplifiers 114-1 to 114-N.

The second inputs of the OR gates 116-1 to 116-N are connected to lines136-1 to 136-N so that the pattern memory can also be filled directly bysignals provided by a computer or read from a data carrier. When suchdata are read into the pattern memory 120, addressing is carried out viathe second inputs of the OR gate 130 which is connected to a line 138.

Associated with the pattern memory 120 is a control circuit 140 which,in dependence upon a control signal transmitted via a line 142 from amain control unit, supplies a signal to a read-in activation terminal IEor to a read-out activation terminal OE.

The control system shown in FIG. 7 operates as follows:

In a first learning mode, the control signals generated by thediscriminator circuits 112 on the basis of the output signals of thesensor elements 110 are stored, as addressed by the rotary encoder 122,in the pattern memory 120, the summing circuit 126 causing the storedsignals in the pattern memory 120 to correspond to those obtained if thesensor strip 108 indicated by broken lines were in the position shown bysolid lines in FIG. 5, that is to say were at the same distance from thenip as was the nozzle strip 62.

In a second type of learning mode, corresponding control signals aretaken via the lines 136 and placed in the pattern memory as addressed bythe signals on the line 142.

In order to powder printed products, the memory cells of the patternmemory 120 are read out as addressed by the rotary encoder 122, thehigher ranking control system not shown in FIG. 7 ensuring that there isno signal on the line 128, so that the unaltered output signal of theanalogue-to-digital converter 124 is obtained at the output of thesumming circuit 126.

As a modification of the illustrative embodiment described above withreference to FIG. 5, it is also possible to provide (where appropriatein addition) a blowing pipe 44 having delivery nozzles that can becontrolled in a similarly separate manner to the nozzles 66 of thenozzle strip 66. The delivery nozzles are then actuated in a mannersimilar to that described above for the nozzles 66 with reference toFIG. 6 or 7, but with the altered phase position with respect to thesensor strip being taken into account. In the modified illustrativeembodiment of the powdering apparatus shown in FIG. 6, instead of anozzle strip 72, a magnetic brush 144 similar to that used to applytoner particles to the drums of photocopiers and laser printers isprovided.

The application roller 38 then carries on its circumferential wall, inaddition, a light-sensitive layer 146. Provided upstream of the magneticbrush 144 is a corona wire 148 and a light-emitting diode strip 150. Theindividual light-emitting diodes or groups of light-emitting diodes ofthe light-emitting diode strip 150 are actuated in a manner similar tothat described above for the solenoid valves 104.

The magnetic brush 144 is arranged at the slot-shaped lower delivery endof the powder reservoir 68 and takes powder particles from the latter,which powder particles are transferred by the magnetic brush 144 to thenon-exposed portions of the layer 146 as is usual in photocopying. Thepowder-coated regions of the application roller 38 then deliver thepowder particles to the printed products in the nip. An applicationroller of that kind is considerably larger in size than thephotoconductive drum of a photocopier. Since, however, a high resolutionis not required in the selective regional powdering of printed productsand since also the particles to be transferred are far larger than tonerparticles, cheaper materials can be used for the photoconductive layer146 than for photoconductor drums.

In the further modified illustrative embodiment shown in FIG. 9, thesupport roller 32 has been replaced by a second application roller 38'of a powder application head 30' that is symmetrical to the powderapplication head 30. In that manner, the printed products can be evenlypowdered from both sides.

I claim:
 1. Apparatus for powdering printed products in a printingmachine through which the printed products are moved by gripper rods(24) comprising:a flexible conveyor (22), gripper rods (24) carried bythe flexible conveyor (22), a reservoir (68) for powder material, adevice (70) for delivering a metered powder stream from the reservoir(68), an application head (30) which applies the metered powder streamto the printed products moved past it, the metered powder stream beingdistributed over the width of the printed products, the application head(30) having an application roller (38), a powder feeding element (62,144) cooperating with the application roller (38) and being loaded withthe powder stream by the delivery device (70) and distributing thepowder stream over the length of the application roller (38), and asupport element (32, 38) which supports the reverse sides of the printedproducts, the circumference of the application roller (38) correspondingto the distance between successive gripper rods (24) on the flexibleconveyor (22) and having at least one axial surface recess (52) capableof receiving the gripper rods (24) at least partially, thecircumferential surface of the application roller (38) being tangentialto the path of the printed products, the powder feeding element (62,144) being arranged upstream of the nip defined by the applicationroller (38) and the support element (32, 38') viewed in direction ofrotation, the powder material transferred to the printed products beingcarried by the surface of the application roller (38), and the printedsides of the printed products being in positive mechanical contact withthe application roller (38), while being moved between the applicationhead (30) and the support element (32, 38').
 2. Apparatus according toclaim 1, characterised in that the support element (32; 38') runs at thesame speed as the application roller at the passage nip.
 3. Apparatusaccording to claim 1, characterised in that at least the applicationroller (38), and where applicable the support element (32; 38') also, isrigidly connected to a drive part (56, 58) that cooperates with one ofthe flexible conveyor means (22).
 4. Apparatus according to claim 2,characterised in that the support element (32; 38') is a support roller.5. Apparatus according to claim 4, characterized in that, the supportroller (32; 38') is provided with an axial surface recess (52, 54) inwhich a gripper rod (24) can be received at least partially, the phaseposition of support roller (32; 38') and application roller (38) beingclosely coupled for moving their surface recesses (52, 54) through thepassage nip simultaneously with a gripper rod (24).
 6. Apparatusaccording to claim 1, characterized by a suction device and a housing(36) which surrounds the application roller (38), the interior of whichhousing is connected to the suction device (90, 92).
 7. Apparatusaccording to claim 1, characterized by a housing (36) surrounding theapplication roller (38) having a coaxial housing wall (82) accompanyingthe outer surface of the application roller (38) and spaced with a smallclearance with respect to the support element (32).
 8. Apparatusaccording to claim 1, characterized by a source of negative pressure (98to 102), the application roller (38) being hollow and having acircumferential wall (82) made from a material that is permeable to airbut impermeable to powder, the interior of the application roller (38)being connected to the source of negative pressure (98 to 102). 9.Apparatus according to claim 1, characterised in that a blowing strip(84) is arranged in the interior of the application roller (38) in thevicinity of the passage nip.
 10. Apparatus according to claim 1,characterized by a mixing device (72), wherein the powder feedingelement (62) is a nozzle strip connected to the outlet of the mixingdevice (72) which mixes the metered powder stream produced by thedelivery device (70) with a carrier gas stream.
 11. Apparatus accordingto claim 1, characterized in that the powder feeding element is a brushroller, which is loaded with the metered powder stream at a firstcircumferential portion and contacts the surface of the applicationroller (38) at another circumferential portion.
 12. Apparatus accordingto claim 1, characterized by a housing (36) surrounding the applicationroller (38), and a barrier air blowing strip (84) on the housing (36)upstream of the feeding element (62) viewed in the direction ofrotation, which produces a radially oriented air curtain.
 13. Apparatusaccording to claim 1, characterised by a feeding electrode (94) whichextends in the axial direction of the application roller (38) and avoltage generator (96) one terminal of which is electrically connectedto the feeding electrode (94) and the other terminal of which iselectrically connected to the application roller (38).
 14. Apparatusaccording to claim 1, characterized by a control unit (106) and a powderrelease element (44), the powder feeding element (62) and/or the powderrelease element (44) being arranged at the passage nip and having aplurality of operating segments that are activated independently of oneanother and actuated by the control unit (106) to dust the printedproducts with powder only in given regions.
 15. Apparatus according toclaim 14, characterised in that the control unit (106) comprises apattern memory (120) which contains the activation signals for theoperating segments (66) for one revolution of the application roller(38) and which is addressed in accordance with the instantaneous angularposition of the application roller (38).
 16. Apparatus according toclaim 15, characterized by a sensor strip (108) extending transverselyacross the path of the printed products and having sensor elements (110)which provide a plurality of measurement signals associated with the inkthickness of the respective transversal regions of the printed productbeing monitored by the sensor elements (110), and by a read-in controlunit for the pattern memory which stores the measurement signals in thepattern memory (120) with addressing of the pattern memory (120) inaccordance with the instantaneous angular position of the applicationroller (38).
 17. Apparatus according to claim 16, characterised by adiscriminator arrangement (112) which is connected between the outputsof the sensor strip (108) and the pattern memory (120).
 18. Apparatusaccording to claim 14, characterized in that the feeding element (62)has a plurality of operating segments (66) which are activatedindividually, characterized by a sensor strip (108) having a pluralityof sensor elements (110) arranged upstream of the passage nip, whichsensor strip provides a plurality of measurement signals associated withthe ink thickness of the respective region of the printed product lyingin front of the sensor elements, the measurement signals each serving toactuate an associated operating segment (66).
 19. Apparatus according toclaim 1, characterised in that the support element is formed by a secondapplication head (30'), the first application head (30) and the secondapplication head (30') operating in a functionally identical manner andpreferably being constructed symmetrically to the conveying surface ofthe printed products.
 20. Apparatus according to claim 8, wherein thematerial comprises a sintered material of plastics material. 21.Apparatus according to claim 12, the barrier air blowing strip producingan air curtain that is oriented radially and in the direction ofrotation of the roller.
 22. Apparatus according to claim 11, wherein thebrush roller comprises a magnetic brush roller formed by magneticparticles and a rod-shaped radially magnetized permanent magnet. 23.Apparatus according to claim 18, characterized by a discriminatorcircuit (112) associated with each of the sensor elements (110) thatmodifies the measurement signals.